Means for positioning lantern slides



0a. 13,1942. C, D Rm 1 2,298,413

MEANS FOR POSITIONING LANTERN SLIDES Filed April 24, 1941 JI-/- iCHARLES D. REID INI/EN TOR Patente-d Oct. 153 1942 MEANS FOR POSITIONINGLANTERN SLIDES Charles D. Reid, Rochester, N. Y., assigner to EastmanKodak Company, Rochester, N. Y., a corporation of New Jersey ApplicationApril 24, 1941, Serial N0. 390,139

3 Claims.

This invention relates to projection and more particularly to slidecarriers for positioning picture carrying elements in a projector.

One object of my invention is to provide a picture carrier in whichlantern slides of diierent thicknesses may be used. Another object of myinvention is to provide a carrier of the class described which mayaccurately position lantern slides of two different thicknesses andwhich will position other lantern slides close to the proper position sothat the minimum amount of focusing will be necessary when using dierenttypes of lantern slides. Still another object of my invention is toprovide a lantern slide holder in which the lantern slides arepositioned by pairs of opposing walls arranged at diiierent angles sothat a slide of one thickness will be positioned in one position in thecarrier and a slide of another thickness will be positioned in anotherposition in the same carrier.

It is well known that lantern slides, because of their construction, mayvary widely in thickness, For instance, one of the most popular type oflantern slides consists of a cellulosic support having apicture-carrying element on one side, this support being carried in alight cardboard or paper frame. It is usually customary to varnish thepicture carrying element so that finger prints will not readily betransferred to it. Such a lantern slide is quite thin. They are popularbecause they are extremely inexpensive.

A second known type of lantern slide consists of a cellulosic supportcarrying a picture element on one side, this picture-carrying elementbeing protected by a sheet of clear glass. 'Ihe picture-carrying elementmay be cemented to the glass or there may be two protecting pieces ofglass one on each side of the picture-carrying element. If more than onesheet of glass is used a metallic binder or a tape binder may be used,so that it will be seen that there is normally a number of dierentthicknesses of lantern slides which may be used in the same projector.

Coming now to the drawing wherein like reference characters denote likeparts throughout:

Fig, 1 is a front elevation of a lantern slide carrier constructed inaccordance with and embodying a preferred form of my invention.

Fig. 2 is a top plan view of the carrier shown in Fig. 1.

Fig. 3 is an enlarged fragmentary detail section taken on line 3-3 ofFig. 1.

Fig. 4 is an enlarged fragmentary detail section similar to Fig. 3, butshowing a portion of a slide lof greater thickness in place.

Fig. 5,is an enlarged detail fragmentary section taken on line 5-5 ofFig. 1.

My invention is directed broadly to a lantern slide carrier which willaccurately position at least two dilerent thicknesses of lantern slidesand which will position still other thicknesses of slides inapproximately the best position for projection.

To accomplish this, I provide a pair of spaced rails which supportstandard lantern slides by their opposite edges, each of the railsconsisting of a pair of walls arranged at different angles with respectto the carrier so that while one type of slide may be centered in theholder, a second type of slide may be decentered by an amount which willcompensate for the thickness of the slide.

More specifically, I provide a lantern slide carrier which consists of abase plate or bar I which supports upstanding ends 2 and which maysupport an upstanding center member 3. On each end 2 of the lanternslide carrier, I provide a rail designated broadly as 4 for supportingone edge of a lantern slide. This rail may be formed up from sheet metaland may include two side walls -5 Yembracing the edges of the upstandingend 2 and having a slidable connection therewith through the studs 6which pass through slots I in member 2 so that the rails may slide backand forth in seats 8 which may be conveniently countersunk in the endmembers 2. 'Ihe end members 2 have a central bore 9 supporting a coilspring I0 which bears against and exerts an outward thrust upon alantern slide, which may be designated broadly as L. The edge E of thelantern'slide may be positioned by means of a pair of angularly disposedwalls II and I2, the angle of wall II being different from the angle ofwall I2 with respect to the lantern slide base plate I.

I prefer to attach a guide plate I3 to one side of the rail member 5 andto form this inwardly and outwardly, as illustrated at I4, to provideguiding edges which, as best shown in Fig. 1, will project above theends of the angularly disposed walls I2 and Il. These facilitate loadinga lantern slide L into position in a darkened room, since one edge ofthe lantern slide may be rested upon the forming I4 before moving itdownwardly between the supporting rails. The upstanding center member 3is also provided with a rail which guides the opposite edge of thelantern slide holder L, this rail, indicated broadly as I5, beingpreferably attached by rivets I5a so that it will be immovable. As shownin Fig. 2, the xed rail is also provided with a pair of angularlydisposed walls I6 and I'I which are preferably of the same angles aswalls I2 and II-that is, the angles of walls I2 and I6 are the same andthe angles of walls II and II are the same.

Fig. 3 illustrates a slide L of the most inexpensive type. This slidemay consist of a support S carrying on one side a picture P, there beingon both sides of the picture-carrying element and support lightcardboard or paper frame members F. The total thickness of this slide iscomparatively slight and the picture-carrying side of the slide isspaced a distance d from the front edge wall of the picture carrier-thatis, the edge wall which faces the projectionlens,

In Fig. 4, I have illustrated' another known type of lantern slide,designated broadly asL, this slide also including a support S', carryinga picture P' on one side. In this case there are two sheets of glass Gwhich cover both sides of the picture-carrying element and all of theseparts are held together by means of a binding B around the edges of theglass plates.

The angular relation of the walls I I and I2 and I6 and I'I is soselected that when a thick slide L is positioned between these walls,the distance D from the front wall of the holder to the picture-carryingelement will be spaced from the projector lens a distance T greater thanthe picture-carrying element P of the thin lantern slide L. The reasonfor this is that in Fig. 4, the distance T is approximately equal toone-third of the glass plate G lying between the picture-carryingelement and the objective and the distance T is selected so that itcompensates for the refractive index of the glass. Therefore, if the'lantern slides L' and L are both used in the same projector, it isunnecessary to focus the projector, even though these lantern slides areof quite different thickness and construction.

I prefer to design a lantern slide carrier so that it will accuratelyposition two standardv types of lantern slide and so that at least twotypes can be used without focusing.- However, it happens that if this isdone, the angular relationship of the walls II and I2 and I6 and I'I issuch that it approximately positions the other standard types of lanternslides in approximately the proper plane, so that lantern slides ofother known constructions can be used even though slight focusing may benecessary for some of them.

Actually, it is practically impossible to design a lantern slide carrierwhich would take care of all known types of lantern slides, because thedistance T depends on the refractive index of the particular glass whichmay be used. The required spacing can be determined by the formula N-lwhere N is the refractive index of the glass. The glass normally usedfor lantern slides must be of fair quality and such ordinary glass has arefractive index of approximately one and onehalf. Of course, differentgrades of glass can be used having a different refractive index, butthis can be taken as substantially the standard type ofematerial formaking lantern slides.

I am aware that lantern slide Aholders have been suggested in which thetwo opposed edges of a lanternslide are held by a pair of rails having aV-shape in cross-section, but such holders have proposed oppositeangular walls having the same angular relationship to the supportingplate for Cil the lantern slide holder. When the same angularrelationship exists between both sets of walls, it will tend to centerthe picture-carrying element with respect to the holder so that apicturecarrying element utilizing a glass plate for protection on theside facing the objective will be out of focus by a distance ofapproximately onethird of the glass plate. Consequently, such lanternslide holders do not accomplish the same purpose as the lantern slideholder which I have described above.

At the present time, the lantern slide holders of a 2" x 2 size aregenerally one of two types, iirst,and most extensively used, a lanternslide holder made without glass, in which paper frames support acellulosic picture-carrying element.

Second, the samertype of picture-carrying ele- Vment is used sandwichedbetween a pair of glass plates. The thickness of these glass plates issubstantially uniform, so that by designing a lantern slide holder withrails formed by two an- -gularlyV disposed walls, one having a greaterinclination relative to the slide holder than the other, I can lprovidea lantern slide carrier which can be used with the two main types oflantern slides without focusing, even though the thin or thick slidesare used one after the other. If it should happen that certain slideshave much thicker glass protection, the projector would have to befocused, but the focusing movement required would be less than would berequired in the Ausual type of vholder where the picture-carryingelement is always centered with respect to the lantern slide carrier orwhere the picturecarrying element is always in the same position withrespect to the lantern slide carrier.

I claim: Y

1. AA holder forpicture carrying slides for use in projectors includinga source of light andan objective, said slides including picturecarrying elements with or without a coverglass of known thickness, saidholder including, in combination, a base' plate, a pair of spaced railson the base plate in spaced relationship, at least one rail beingmovably mounted, a spring tending to press the movably mounted railtowards the opposite spaced rail, each railincluding a pair of wallsarranged to form a substantially V-shaped groove, the' walls beingunsymmetrical, the angle of one rail-,being greater than the angle ofthe facing rail with respect tothe slide holder, whereby a slide may beheld t0 one side of the center of the spaced rails for projection, theinclination of one wall relative to the other wall being selected tospace the picture-carrying element of a glass covered slide further fromthe objective of a projector than the picture-carrying element of anuncovered slide to compensate at least in part for the difference infocal plane between the two types of slides.

2. A holder for picture carrying' slides for use in projectors includinga source of light and an objective, said slides including a picturecarrying elementy either without glass orv covered by glass of apredetermined thickness including, in combination, a base plate, a pairof spaced rails carried thereby,v means normally' thrusting one railtoward the other,` each rail including a pair of intersecting wallsforming a'substantially V-shaped groove to receive an edge of thelantern slide, the angular inclination of one wall o f each raildiffering from the angular inclination of the opposite wall, theinclination'of the two walls being sov selected as toposition a slidecovered by glass of a known thickness substantially one third of thethickness of the glass further from the objective of a projector inwhich the slide holder is used than said Walls would position apicturecarrying element not covered With glass, whereby thepicture-carrying elements of both slides would lie automatically in theproper focal plane.

3. A holder for picture carrying slides for use in projectors includinga source of light and an objective, said slides including apicture-carrying element either Without glass or covered by glass of apredetermined thickness including, in combination, a base plate, a pairof spaced rails carried thereby, means normally thrusting one railtoward the other, each rail including a pair of intersecting wallsforming a substantially V- shaped groove to receive an edge of thelantern slide, the angular inclination of one Wall of each raildiffering from the angular inclination of the opposite Wall, each of thefacing pair of rails including Walls facing the front of the slidecarrier of one inclination and each of the facing pairs of railsincluding Walls facing the back of the slide carrier including rails ofthe same inclination but differing from the inclination of the railsfacing the front of the carrier, whereby said rails may position thepicture carrying elements of uncovered slides in one position and mayposition glass covered slides in another position with respect to oneedge of the slide carrier to eliminate or minimize focusing of aprojector in which said different slides may be used.

CHARLES D. REID.

